The present invention is for a collapsible boat which is extremely lightweight and easy to assemble. The collapsible boat has particular utility for use as a kayak.
Collapsible boats such as canoes and kayaks have classically had a frame which supports a skin which forms the hull of the boat. The skin is frequently loosely fitted over the frame, and then tensioned over the frame by inflatable chambers either contained in the skin or positioned between the skin and the frame. When the chambers are inflated by the user, the skin is tightened over the frame to provide rigidity to the resulting boat.
In the case of folding kayaks, the skin is formed with a deck which limits the ability to fit the skin over the frame, since the skin completely surrounds the frame at the ends. In such case, the frame is typically formed in two halves which are inserted into the skin and then assembled together. In some designs, the connection of the frame halves together also serves to expand the frame longitudinally, providing some degree of tension against the skin.
The use of an independent, free-standing frame complicates the structure of the boat and increases weight. In the case of canoes, which typically lack decks, it has been found advantageous to employ the tension of the skin to secure the frame elements together. Such boats are taught in U.S. Pat. Nos. 5,915,327 and 6,314,904, by the inventor of the present invention. These boats employ a frame having a telescoping keel stringer, and the frame is expanded longitudinally by the action of supplemental stringers. The supplemental stringers forcibly engage the telescoping keel stringer at each end and increase the effective length of the telescoping keel stringer as the supplemental stringers are fitted into position with respect to the other elements of the frame. The increased length of the telescoping keel stringer acts to tension the frame against the skin longitudinally. Further tensioning of the skin over the frame is provided by inflatable compartments. While such boats have achieved significant reductions in weight, further simplification of the frame structure would be advantageous to further reduce weight and to facilitate fabrication. Additionally, the end structure employed in these boats limits the shape of the ends to a relatively broad curve, limiting the visual appearance of the resulting boat and making fitting a deck to the boat for use as a kayak problematic.
Thus, there is a need for a collapsible boat having reduced weight and a simplified structure. There is also a need for a lightweight collapsible boat which is suitable for use as a kayak.
The collapsible boat of the present invention has a frame which is covered by a hull skin. The frame includes a pair of gunwales, each having a gunwale first end and a gunwale second end, and a series of ribs, each of which is attached to the gunwales by gunwale-engaging clips. The frame also includes a keel stringer, which terminates at a first stem element and a second stem element. The first stem element terminates at a first stem element end, while the second stem element terminates at a second stem element end.
Preferably, the gunwales and the keel stringer are each formed of multiple pieces of tubing, slidably connectable and maintained together with shock cord in the manner known in the art for forming collapsible tubular members. The ribs are preferably each formed of a single piece of tubing. The keel stringer has rib-engaging clips affixed thereto, to which a central portion of each of the ribs can be lockably engaged. Preferably, each rib has a clip-engaging attachment designed to lockably mate with one of the rib-engaging clips of the keel stringer. Such rib-engaging clips and clip-engaging attachments are described in U.S. Pat. No. 6,314,904 of the present inventor, incorporated herein by reference.
Means are provided for securing the gunwale first ends with respect to the first stem element end and for securing the gunwale second ends with respect to the second stem element end. These means complete the formation of the frame and, when longitudinal tension of the frame against the hull skin is provided, these means allow such longitudinal tension to secure the various elements of the frame together.
One aspect of the present invention resides in a preferred structure for securing the gunwale first ends with respect to the first stem element end. With this preferred structure, each of the gunwale first ends has a first end connector which is connectable to the first stem element end. Preferably, the first end connectors are freely movable into engagement with the first stem element end from above, and the first stem element end supportably engages the first end connectors to prevent further upwards motion of the first stem element with respect to the gunwale first ends.
The connection of the gunwale first ends to the first stem element end can be facilitated by the use of a first bracket attached to the first stem element end, in which case the first end connectors are designed to be connectable with the first bracket. In a preferred embodiment, the first bracket has a pair of upwardly-opening slots and the first end connectors are formed by bolts with shanks sized to slidably engage each of the slots, while the heads of the bolts are sized to retain the bolts in the slots.
Alternatively, the first stem element end can be directly engaged by the first end connectors on the gunwale first ends. In one preferred embodiment, the first stem element end has an opening, and the first end connectors are formed with pins which are insertable into the opening.
A similar structure can be employed for securing the gunwale second ends with respect to the second stem element end, in which case the gunwale second ends each have a second end connector thereon which is connectable to the second stem element end.
The hull skin of the collapsible boat has a pair of gunwale sleeves which slidably engage the gunwales of the frame. The hull skin also has a pair of side panels attached to the gunwale sleeves, and a bottom panel attached to the side panels. The side panels and the bottom panel are configured to secure the side panels to each other at the ends of the boat. Preferably, the bottom panel has bottom panel extensions at each end to which the side panels are attached, the bottom panel extensions forming the regions of the hull skin which overlie the first and second stem elements.
Another aspect of the present invention resides in the optional use of the hull skin to secure the gunwale ends to the corresponding stem element end at one or both ends of the collapsible boat, this option being discussed hereinafter in terms of the gunwale second ends and the second stem element end. When this option is employed, the means for securing the gunwale second ends is provided by closed sleeve ends on the gunwale sleeves in combination with means associated with the hull skin for securing the gunwale second ends together and preventing upwards motion of the second stem element end. The closed sleeve ends of the gunwale sleeves limit the longitudinal position of the gunwales with respect the gunwale sleeves by blocking motion of the gunwales when the gunwale second ends are engaged with the closed sleeve ends. Preferably, the gunwale second ends are engaged by the closed ends when at a position where they reside in close proximity to the second stem element end after the frame is assembled. The means for securing the gunwale second ends together and for preventing upwards motion of the second stem element end act both to maintain the gunwale second ends in close proximity to each other and to limit any upward motion of the second stem element end. The use of the closed sleeve ends serves to provide greater accuracy in alignment between the frame and the hull skin, and can be employed in collapsible boats having various means for securing the gunwale first ends with respect to the first stem element end.
The closed ends of the gunwale sleeves can be made permanently closed, such as by sewing or, as discussed in greater detail below, by use of a fastener to secure the fabric of each of the gunwale sleeves together to close the ends.
Alternatively, the closed ends can be provided by an openable closure element associated with each gunwale sleeve which can close the end of the sleeve when secured, but which can be opened to allow slidable engagement between the gunwale and the gunwale sleeve. Having at least the closed ends of the gunwale sleeves openable at one or both ends of the boat allows the use of this aspect of the present invention at both ends of the boat, since the gunwale sleeves can be opened at one end to allow the gunwale sleeves to be inserted therein, and thereafter closed to limit the position of the gunwales. In one preferred embodiment, each gunwale sleeve is provided with a closure flap which extends over the end of the gunwale sleeve and is securable to the gunwale sleeve to close the end. The engagement of the flap with the gunwale end limits the position of the gunwale with respect to the gunwale sleeve.
In one preferred embodiment employing the closed sleeve ends, the means for securing the gunwale second ends together and preventing upwards motion of the second stem element end is provided by a cross strap that is attached to the hull skin and extends over the gunwale sleeves in the vicinity of the closed sleeve ends. The cross strap secures the gunwale second ends together when the gunwale second ends are positioned at the closed sleeve ends of the gunwale sleeves. The closed sleeve ends of the gunwale sleeves in this embodiment are positioned such as to place the gunwale second ends above the second stem element end when the collapsible boat is assembled. Thus, the gunwale second ends are positioned to engage the second stem element end (through the fabric of the gunwale sleeves) to limit any upwards motion of the second stem element end. Since tension of the frame against the hull skin creates an upwards force on the second stem element, the skin tension causes the second stem element end to forcibly engage the gunwale second ends so as to be secured with respect thereto.
In another preferred embodiment employing the closed sleeve ends, the means for securing the gunwale second ends together and for preventing upwards motion of the second stem element end are provided by a fold in the hull skin in close proximity to the closed sleeve ends of the gunwale sleeves in combination with a fastener that secures the fold in the hull skin together. By securing the fold together, the fastener secures the closed sleeve ends of the gunwale sleeves together and thus acts to secure the gunwale second ends together. As noted above, when the closed ends of the gunwale sleeves are to be permanently closed, the fastener can also serve to provide the closed ends of the gunwale sleeves by securing the fabric of the gunwale sleeves together. When a fold in the hull skin secured by a fastener is employed, the fastener also acts to form a pocket into which the second stem element end seats to prevent upwards motion of the second stem element end. Again, skin tension creates an upwards force on the second stem element, and in this embodiment causes the second stem element end to forcibly engage the pocket so as to be secured therein. Thus, in this embodiment the gunwale second ends are secured with respect to the second stem element end via the hull skin.
Means for longitudinally tensioning the hull skin with respect to the frame are provided. The tension of the hull skin maintains the gunwales engaged with the gunwale-engaging clips on the ribs, and typically also respectively maintains the gunwale first ends and the gunwale second ends secured with respect to the first stem element end and the second stem element end. One means for longitudinally tensioning the hull skin with respect to the frame is to employ a telescoping keel stringer in combination with supplemental stringers which act to lengthen the telescoping keel stringer as the supplemental stringers are moved into position, such as taught in the ""904 patent.
However, another aspect of the present invention provides a simpler structure for longitudinally tensioning the hull skin with respect to the frame, which eliminates the requirement for supplemental stringers and the structure required to connect the supplemental stringers to the telescoping keel stringer at each end. The collapsible boat with this simplified structure uses the keel stringer to longitudinally tension the hull skin against the frame. This improved structure for longitudinally tensioning the hull skin with respect to the frame can be used with the structures discussed above for securing the gunwale ends with respect to the stem elements, or with the structures for securing the gunwale ends employed in earlier collapsible boats, such as are taught in the ""904 patent and U.S. Pat. No. 5,915,327, also incorporated herein by reference. In all cases, the keel stringer is formed with a joint spaced apart from the first stem element and the second stem element so as to reside in a central region of the collapsible boat, hereinafter referred to as a central joint. When the keel stringer is formed of multiple sections of tubing, the central joint can be readily provided between two of the sections. The keel stringer is installed while in a bent configuration where the sections of the keel stringer on either side of the central joint are substantially inclined with respect to each other. After installation in its bent configuration, the keel stringer can be straightened to increase its effective length in order to longitudinally tension the hull skin.
When the keel stringer is installed in its bent configuration, the gunwale first ends can be secured with respect to the first stem element end without resistance due to skin tension. For example, when the collapsible boat employs a first bracket on the first stem element end as discussed above, the first end connectors of each of the gunwales can be readily connected to the first bracket on the first stem element while the keel stringer is in its bent configuration. Similarly, when the means for securing the gunwale second ends is provided by the frame of the collapsible boat, the gunwale second ends can readily be secured with respect to the second stem element end while the keel stringer is in its bent configuration. In the alternative case, where the gunwale second ends are secured with respect to the second stem element end by employing closed sleeve ends on the gunwale sleeves, the second stem element end can be positioned with respect to the hull skin and the gunwale second ends so as to become secured with respect thereto when the keel stringer longitudinally tensions the hull skin.
After the stem elements have been positioned for securing to their respective gunwale ends, one of the ribs, which is located at or near the center of the collapsible boat and is hereinafter referred to as a central rib, is connected to the gunwales. The keel stringer is then moved to a substantially straight configuration where the sections of the keel stringer on either side of the central joint are substantially aligned. The keel stringer is also moved to a central location, where it can lockably engage the central rib at a point near the central joint. It should be appreciated that, when the keel stringer is first placed into its substantially straight configuration, its effective length is typically limited by tension from the skin, which maintains the keel stringer bowed at a somewhat reduced length. As additional ribs are installed and lockably engaged with the keel stringer, the keel stringer is increasingly forced into a straight configuration, increasing its effective length. The increased length of the keel stringer as it is moved from its bent to its substantially straight configuration and then brought to its straight configuration causes the stem elements and the gunwales to forcibly engage the hull skin, thereby tensioning the hull skin longitudinally against the frame.
In one preferred embodiment, the central joint is formed between two adjacent sections of the keel stringer, one of which is provided with an insertable section. The insertable section of the central joint is inserted into the adjacent section of the keel stringer to place the keel stringer in its substantially straight configuration. The insertable section preferably has a rounded profile, which allows the user to readily insert the insertable section into the adjacent section of the keel stringer while the keel stringer is in its bent configuration.
The use of the jointed keel stringer discussed above greatly simplifies the structure of the collapsible boat. This simplified structure decreases the cost of fabrication, facilitates assembly and disassembly of the boat, and reduces the size and weight of the boat when the boat is collapsed for storage and/or transport. This structure also reduces the area of the hull skin which is subjected to significant abrasion.
While the longitudinal tension of the hull skin over the frame is typically sufficient to maintain the elements of the frame secured with respect to each other, it is preferred to also provide transverse tension of the hull skin over the frame to provide increased rigidity for the collapsible boat. Such transverse tension can be provided by a pair of inflatable compartments which reside between the side panels of the hull skin and the frame when the collapsible boat is assembled. When inflated, the inflatable compartments maintain the hull skin tautly in place on the frame such that the frame and the hull skin act together to form a self-supporting structure. The transverse tension acts to further secure the elements of the frame to each other to allow use of the collapsible boat in rough water conditions. When the inflatable compartments are deflated, the hull skin more loosely engages the frame to facilitate assembly and disassembly.
When the frame of the collapsible boat employs a single keel stringer with a central hinge as discussed above, the inflatable compartments are also preferably sized and configured to provide a smooth contour of the hull skin with respect to the ribs of the frame.
When the boat is to be used as a kayak, it has a first deck support member which attaches to the frame such that the first deck support member extends parallel to the ribs. A first deck stringer is also provided, having a first deck stringer inner end region, which is configured to engage the first deck support member, and a first deck stringer outer end region, which is configured to reside above said gunwale first ends. Means are provided for securing the first deck stringer outer end region with respect to the gunwale first ends, these means being associated with the hull skin. Similarly, a second deck support member attached to the frame so as to extend parallel to the series of ribs, and a second deck stringer is provided which has a second deck stringer inner end region, which engages the second deck support member, and a second deck stringer outer end region, which resides above said gunwale second ends. Means are provided for securing the second deck stringer outer end region with respect to the gunwale second ends, these means again being associated with the hull skin.
A deck skin is provided to extend over the frame to close the top region of the hull skin, and is supported over the first deck support member, the first deck stringer, the second deck support member, and the second deck stringer. These elements preferably maintain the deck skin in a convex or peaked configuration to prevent pooling of water thereon. The deck skin attaches to the hull skin below the gunwales, preferably by snaps or hook-and-loop fasteners. The deck has a cockpit opening located in a central region to allow a user to sit in the collapsible boat.
The first deck support member and the second deck support member can be attached either directly to the gunwales or to one of the ribs in close proximity to the gunwale-engaging clips. Alternatively, the first deck support member and the second deck support member could each be made an integral part of one of the ribs.
Preferably, the hull skin is formed with a first hull skin extension, which extends over the first deck stringer outer end region, and a first deck support strap is attached to the first hull skin extension. The first deck support strap connects the first hull skin extension with respect to the first deck support member, thereby forcibly engaging the first deck stringer outer end region against the gunwale first ends to provide the means for securing the first deck stringer outer end region. A second hull skin extension and a second deck support strap can be similarly employed to provide the means for securing the second deck stringer outer end region with respect to the gunwale second ends. When the bottom panel of the hull skin is provided with bottom panel extensions to which the side panels are attached, the bottom panel extensions can be lengthened to provide the first hull skin extension and the second hull skin extension.
The cockpit opening of the deck skin is preferably surrounded by a raised coaming to deflect water away from the cockpit opening and to allow the user to attach a spray skirt to seal the cockpit opening. In one preferred embodiment, the deck skin is provided with a coaming sleeve which surrounds the cockpit opening, and a tubular coaming member resides in the coaming sleeve. The tubular coaming member can be formed as a two-part structure of aluminum tubing, the two parts being connected together by hinges to allow the tubular coaming member to be folded. The coaming sleeve is preferably formed of an elastic fabric such as neoprene to prevent wrinkling and provide a smoother appearance for the raised coaming.
To provide increased internal space in the collapsible boat, it is preferred to employ longitudinal members which limit the expansion of the inflatable compartments in the spaces between the ribs. Such can be accomplished over the length of the collapsible boat, through use of side stringers which are supported on the ribs, or by side rods connected between desired ribs to limit expansion of the inflatable compartments therebetween.
A boat seat is preferably provided, which can be attached with respect to one or more of the ribs of the frame to maintain the boat seat in position longitudinally. In a preferred embodiment, the boat seat has a seat portion, formed of a first series of inflatable chambers attached to a seat support structure that provides longitudinal rigidity to the seat portion. Preferably, the seat support structure is formed by relatively rigid foam pads which rest on the bottom panel of the hull skin and are positioned on either side of the keel stringer when the boat seat is installed. The foam pads raise the first series of inflatable chambers of the seat portion above the keel stringer for the comfort of the user. The boat seat also has a back portion, formed of a second series of inflatable chambers attached to a back support structure. The seat portion and the back portion are connected together by a fabric hinge, and straps are provided on either side to adjustably limit the rotation of the back portion relative to the seat portion. The straps can also serve to anchor the boat seat to one or more of the ribs to further stabilize the seat with respect to the frame.
To provide leg bracing for the user, particularly when the collapsible boat is used as a kayak, brace straps can be added along the sides forward of the seat. The brace straps should be loose enough to allow the user to readily force their knees thereunder, while being tight enough to provide resistance to allow the user""s legs to become forcibly engaged with respect to the collapsible boat. Such brace straps are known in the art, and are frequently employed in kayaks which are designed for the user to sit atop the deck.